Passing variables between methods in Python?

Question

I have a class and two methods. One method gets input from the user and stores it in two variables, x and y. I want another method that accepts an input so adds that input to x and y. Like so:

class simpleclass(object):
    def getinput(self):
        x = input("input value for x: ")
        y = input("input value for y: ")
    def calculate(self, z):
        print(x + y + z)

When I run calculate(z) for some number z, it gives me errors saying the global variables x and y aren't defined.

How can calculate get access to the x and y values that were assigned in getinput?

Does this answer your question? [How to share variables between methods in a class?](https://stackoverflow.com/questions/7670415/how-to-share-variables-between-methods-in-a-class) — outis, Dec 19 '21 at 19:39
@outis it's close, but I decided this is the better version of the question to use as a canonical. — Karl Knechtel, Oct 23 '22 at 03:45

score 17 · Answer 1 · edited Aug 17 '22 at 06:36

17

These need to be instance variables:

class simpleclass(object):
    def __init__(self):
        self.x = None
        self.y = None

    def getinput(self):
        self.x = input("input value for x: ")
        self.y = input("input value for y: ")
   
    def calculate(self, z):
        print(self.x + self.y + z)

edited Aug 17 '22 at 06:36

Karl Knechtel

62,466
11
102
153

answered Mar 01 '12 at 16:33

turtlebender

1,907
15
16

2

+1 for most correct answer illustrating use of the __init__() method. – Li-aung Yip Mar 01 '12 at 16:38

score 5 · Answer 2 · edited Aug 17 '22 at 06:37

5

You want to use self.x and self.y. Like so:

class simpleclass(object):
    def getinput(self):
        self.x = input("input value for x: ")
        self.y = input("input value for y: ")
    def calculate(self, z):
        print(self.x + self.y + z)

edited Aug 17 '22 at 06:37

Karl Knechtel

62,466
11
102
153

answered Mar 01 '12 at 16:32

Li-aung Yip

12,320
5
34
49

score 3 · Answer 3 · edited Aug 17 '22 at 06:37

3

x and y are local variables. They get destroyed when you move out from the scope of that function.

class simpleclass(object):
    def getinput(self):
        self.x = input("input value for x: ")
        self.y = input("input value for y: ")
    def calculate(self, z):
        print(int(self.x) + int(self.y) + z)

edited Aug 17 '22 at 06:37

Karl Knechtel

62,466
11
102
153

answered Mar 01 '12 at 16:34

Karoly Horvath

94,607
11
117
176

Probably want to get a number from the string at some point if you're switching to raw_input. – DSM Mar 01 '12 at 16:36

score 2 · Answer 4 · edited Aug 17 '22 at 06:38

2

Inside classes, there's a variable called self you can use:

class Example(object):
    def getinput(self):
        self.x = input("input value for x: ")
    def calculate(self, z):
        print(self.x + z)

edited Aug 17 '22 at 06:38

Karl Knechtel

62,466
11
102
153

answered Mar 01 '12 at 16:33

Brendan Long

53,280
21
146
188

score 0 · Answer 5 · edited Aug 17 '22 at 06:40

class myClass(object):
    def __init__(self):
        pass
    
    def helper(self, jsonInputFile):
        values = jsonInputFile['values']
        ip = values['ip']
        username = values['user']
        password = values['password']
        return values, ip, username, password
    
    def checkHostname(self, jsonInputFile):
       values, ip, username, password = self.helper(jsonInputFile)
       print(values)
       print('---------')
       print(ip)
       print(username)
       print(password)

The __init__ method initializes the class. The helper function just holds some variables/data/attributes and releases them to other methods when you call it. Here jsonInputFile is some JSON. The checkHostname method logs in to some device/server to check the hostname; but it needs ip, username and password for that, which it gets by calling the helper method.

Passing variables between methods in Python?

5 Answers5

Linked

Related